1. Field of the Invention
The present invention relates to the field of telecommunications. More particularly, the invention is concerned with an ATM reference traffic system (ARTS) that records packet information representative of ATM packets transmitted over an ATM network. The system also creates and transmits ATM packets from packet information on a schedule representative of ATM packet transmission over an ATM network using a personal computer with the operating system modified to schedule events with microsecond resolution while providing interrupts on the original periodic basis to the unmodified portions of the operating system.
2. Description of the Prior Art
In the development of more effective telecommunications networks operating in the asynchronous transfer mode (ATM), it is necessary to conduct experiments to evaluate the performance of such networks and the associated equipment. For this purpose, prior art equipment such as the Hewlett Packard J2912A ATM test set has the ability to measure network performance at the ATM cell level. More particularly, this equipment can measure the arrival times of ATM cells over a network in order to provide an indication of delays and missing cells. This information, however, does not allow for reproduction of actual network traffic at network speeds in order to evaluate network performance.
Other equipment in the prior art enables the generation of synthetic ATM traffic generating ATM packets according to probabilistic models. Synthetically generated traffic, however, does not reflect the behavior of an actual ATM network under actual network conditions. In order to overcome these limitations, traces of actual network traffic have been recorded using packet sizes and interarrival times and then used as input to network simulations. Simulations, however, may not reflect accurately the behavior of actual networks.
Another difficulty in evaluating ATM performance is that the test equipment must be able to handle timing with microsecond resolution. Conventional microcomputers have operating systems that operate on a time base of ten milliseconds for providing periodic interrupts. This is much too slow for evaluating the high speed of ATM transmissions. Merely shortening the interrupt interval does not solve the problem because this increases the interrupt service overhead to the point where little processing capacity remains for user processes. As a result, evaluation of ATM networks requires expensive specialized equipment having high speed capability. Even the specialized equipment, however, is primarily for analysis at the ATM cell level and not at the ATM packet level.